获取页面控件的子控件值:
string areaStr = Request.Form[area.UniqueID];
获取用户控件中的子控件的值:
string areaStr = area.SelectedValue;
DropDownList dr = (DropDownList)this.FindControl("area");
areaStr = Request.Form[dr.UniqueID];
DropDownList dr = (DropDownList)this.FindControl("area");
areaStr = Request.Form[dr.UniqueID];